It is common knowledge that great strides have been made in the area of orthopaedic medicine by the use of joint implants. The implants are usually metallic and often have porous surfaces. Not all implants, however, are successfully installed in the patient on the initial attempt, and it may be necessary to try two or more implants of different sizes or curvatures during the implant procedure before the desired fit is realized.
The unsuccessful implant in such cases has generally been discarded. Foreign proteins and lipids remain in the interstices of the porous surface of the implant. They can cause an adverse immune reaction in an implant recipient if the implant were reused in another patient. Up to now, these implants have not been reusable and have been simply discarded. Each implant costs more than $1,000, so the cost of such wasted implants at a hospital having an active orthopaedic practice can amount to many thousands of dollars per year--a significant loss in this era of medical cost containment.
None of the cleaning processes now in use have been successful in assuring the removal of all tissue, bone, proteins and lipids from the porous surfaces of the implant. Hospitals have heretofore used detergents for breaking apart lipid tissue components (but not necessarily for their removal from a porous metal surface), and an ultrasonic cleaning bath to enhance cleaning (see U.S. Pat. No. 3,291,640 as well as "Good Hospital Practice: Handling and Biological Decontamination of Medical Devices", issued by the Association for the Advancement of Medical Instrumentation, 1991). Normally, such cleaning treatments have been performed on smooth medical utensils and equipment, as opposed to porous surface implants or other medical devices inserted into the body and intended to be in contact with tissue). U.S. Pat. No. 4,248,642, which deals with the cleaning of laboratory equipment using sodium hypochlorite is also noted.
In the totally non-analogous art of removing resin paint deposited on carbon resistors, Goodin, U.S. Pat. No. 3,147,148, discloses a multi-step process wherein both sodium hypochlorite and nitric acid washes are used to remove paint and silver from a ceramic core.
Them thus exists a need for a simple and inexpensive process that will make it possible to reuse orthopedic implants and similar medical devices whose porous surfaces have become contaminated with protein tissue, bone tissue and lipids. Typical of such devices are titanium, stainless steel and cobalt chrome alloy implants. The present invention is directed to serving this need.